Create a geometry in FME Data Inspector and use it in FME Workbench

I would like to read data inside a bounding box with FeatureReader, but many times I don't have any bounding box. Thus I need to go to Data Inspector, open a dataset, pan the view to a certain place, move mouse cursor to the corners, write down the coordinates, copy the coordinates to Creator in FME Workbench and connect Creator to FeatureReader.

It would be much easier, if I could create a box geometry in FME Data Inspector, and if FME Workbench would be open at the same time, I could use the box geometry straight in Creator. There could be a parameter in Creator, e.g. "Use the geometry from Data Inspector".